VHF cable

Nov 26, 2008
1,966
Endeavour 42 Cruisin
I need to replace some VHF antenna cable. I have a new piece of coax that I think is good for the application but not sure.
Anyone know this cable...

Belden 9100 Duobond II 75ohm Series 59.

Can't remember what I had this for!

Thanx
 
Sep 25, 2008
7,075
Alden 50 Sarasota, Florida
Didn't look it up but offhand - it's the wrong impedance for both the radio and the antenna.

It will suffice but will increase loss and decrease effective radiated power.
 
Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
What Don says. 75Ω cable is good for TV and Satellite Dish but not radios. What you want is any of these:

RG58/U
RG8X
LMR240

There are a few others but these are the standard cables used in the VHF world. These cables are 50Ω.
 
Nov 26, 2008
1,966
Endeavour 42 Cruisin
Ah...50 ohms, I checked around. Right.
This wire might be left over from tv antenna or from my cell phone booster install.

Time to buy more. Why is it the vast amount of spares are never the right spares?
 

pateco

.
Aug 12, 2014
2,207
Hunter 31 (1983) Pompano Beach FL
That is RG59 cable. I wouldn't use it even for cable TV today. The signal loss per foot at higher frequencies stinks. This cable was used a lot for 550 MHz Cable TV systems in the 70s and is still used for analog security cameras.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Ah...50 ohms... Why is it the vast amount of spares are never the right spares?
WHY DON'T YOU LOOK OVER AT "THE TV REPAIRMAN'S FORUM"S? THERE'S BOUND TO BE SOMEONE WITH 50 THAT WOULD SWAP YOU FOR THE 75 :doh:
 
Jun 1, 2016
156
Hunter 28.5 Lake City, MN
I'm a ham radio operator (45+ years), as well as having a boat. VHF always uses 50 ohm coax. For the 50' run from your radio and up your mast, RG-8X is much easier to work with, and the loss will very acceptable. LMR-400 is much lower loss, but will be VERY stiff and hard to work with. There are some other RG-8U coaxes that have stranded center conductors that would be easier to work with.
Google for a "coax loss calculator" like
http://kv5r.com/ham-radio/coax-loss-calculator/
Here is what I came up with:
Loss Calculations.jpg

2 db loss for the RG-8X isn't bad when you consider that the heavier coaxes can be very difficult to work with. Another thought that would be better would be something like RG-142U, which is a double shielded teflon coated, silver plated coax that has lower loss than the RG8X and is about 1/4" in diameter. It won't age like many other coaxes will. Runs about $1.50/ft.

Mike
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
If you use Times LMR 240 or 400 make sure it's UF or the ultra-flex version. The copper coated solid aluminum center conductor in the LMR-400 especially does not like to be flexed.. The LMR UF versions use a stranded copper center conductor as opposed to solid...
 
Sep 25, 2008
7,075
Alden 50 Sarasota, Florida
Note that tradeoff for flexibility by The use of RG 8x as in the example above results in almost 50% power loss. That might be acceptable close to shore but not in marginal situations where hearing a vessel in distress (or being the vessel in distress) is crucial.